| 摘要 |
To provide a spark plug which exhibits excellent load life performance even when the resistor thereof has been thermally compacted at slightly varied heating temperatures. A spark plug 1 includes an insulator 2 having an axial hole 4 extending therethrough along the axis direction CL1; a center electrode 5 inserted into a front end portion of the axial hole 4; a terminal electrode 6 inserted into a rear end portion of the axial hole 4; a resistor 7 disposed in the axial hole 4 to be located between the center electrode 5 and the terminal electrode 6 and containing at least an electrically conductive material and glass. The resistor 7 contains SiO 2 in an amount of 15.0 mass% or more, B 2 O 3 in an amount of 17.8 mass% to 44.8 mass%, Li 2 O in an amount of 1.2 mass% to 6.3 mass%, and BaO in an amount of 3.5 mass% to 19.9 mass%; and has a ratio by mass of the amount of B 2 O 3 to the total amount of Li 2 O and BaO of 1.43 or higher, and a ratio by mass of the amount of Li 2 O to that of BaO of 0.22 or higher. |
